This invention relates to a ordewire detector for a communications system and more particularly to a detector which can be utilized to recover or detect the presence of an analog or digital orderwire signal.
As one can ascertain, much of the communications equipment which exists in the United States utilizes a particular signal format. This is especially true of military communications systems which generally employ a signal which consists of a data signal with a data rate of 72,000 BPS to 2.304 MBPS. The data signal which is usually a digital signal and can be of many particular formats such as an NRZ signal is linearly added to an orderwire signal in order to provide an effective communications link.
The orderwire signal essentially is a low speed data or voice channel signal which is used for maintenance or setup purposes. As indicated, this particular signal format exists in many military communications equipment such as the conditioned diphase family which is capable of transmitting over a fiber optic cable system and employs the signal format to modulate a light emitting diode or other device and then transmit the combined signal over a fiber optic cable or a fiber optic communications link.
Typical examples of the type of equipment which utilize the above-noted signal is the AN/TTC-42, the SB-3865, the TD-1234, the AN/TRC-170, the AN/TTC-39, the AN/TSQ-111, the AN/MRC-139, and the MD-1026. In any event, in certain of these systems, the orderwire used may be of either a digital or analog type. The digital orderwire signal is known as the system orderwire or combined voice digital orderwire (CVDOW). The analog orderwire is known as a maintenance or analog voice orderwire (AVOW).
As one can therefore ascertain, the data signal which is incorporated in such a system is used with an analog or digital orderwire signal. In any event, certain systems would have either the digital orderwire signal or the analog orderwire signal. Suitable examples of the format will be given. As indicated above, much of these systems utilize fiber optic communications links which are employed to interface the equipment to a fiber optic cable. Therefore, the various types of equipment indicated above are all capable of being interfaced to a fiber optic communications link. This requires reformatting of the signal into a signal which is more compatible with a fiber optic system.
In order to accomplish this, one requires separation and recovery of the orderwire signal from the data signal. As indicated above, since the orderwire signal may the CVDOW or AVOW, identification of the orderwire type of signal is required before recovery can be accomplished. In prior art systems the problem of orderwire detection was accommodated either by using a manually operated switch to specify digital or analog orderwire or using digital counters which operate to compare bits and to maintain a digital count of the results and then operating to compare alternate bits in the data stream. This technique was expensive and complicated.
It is, therefore, an object of the present invention to provide a low cost reliable circuit which will enable one to detect the nature of the orderwire signal and therefore to permit efficient recovery of both the digital data signal and the orderwire signal.